The present disclosure relates generally to over-center spring mechanisms. Over-center spring mechanisms are typically used to mechanically hold a pivoting structure in selected resting positions relative to a pivot point. These mechanisms typically include a tension spring that is attached at one end to a fixed structure, and at the other end is attached to the pivoting structure. The position of the spring is such that the spring extends over the pivot point of the pivoting structure at some point during the range of the motion of the pivoting structure. Consequently, the greatest spring force is experienced at a point where the spring applies no moment to the pivoting structure, thus biasing the structure away from the midpoint of its motion.
The force and motion characteristics of over-center spring mechanisms relate to the strength and size of the spring, the position of its attachment to the pivoting structure, and other intervening structure that may be involved in the mechanism. Where an over-center spring mechanism is configured for vertical motion, the spring can be configured to support the weight of the pivoting structure when in a raised position. This can involve the use of a relatively large and strong spring.